no video after upgrade to fedora 20 (from fedora 19)

Thursday, 2 January 2014

Hi,

i finally upgrade fedora 19 to fedora 20 using fedora-upgrade (fedup had 
issues)

System boot normally. Displaying grub, the fedora logo filling from 
black to white ...and colorized finally.
And just after black screen (like no video signal) in my virtual machine 
(where fedora is installed).

I don't understand where is the problem.
Do you have an idea where could issue be located ?

thx.